Official security forces need sometimes to use armed undercover security officers or policemen amongst crowd or in the public area in general. Usually, the gun or the holster that such undercover officers carry on their body can be noticed in their pocket or under their clothes, and they are in the risk to be discovered. This problem relates in fact to any person who wants to carry a gun and wishes that no one will notice that he carries a gun. The present invention aims to provide an effective and efficient solution for this problem.